TY - JOUR
T1 - Heat stress and thermal dehydration
T2 - Lactacidemia and plasma volume regulation
AU - Zurovski, Y.
AU - Eckstein, L.
AU - Horowitz, M.
PY - 1991
Y1 - 1991
N2 - This investigation was undertaken to study heat stress and dehydration effects on 1) plasma lactic acid (LA) concentration and 2) plasma LA effect on plasma volume conservation during thermal dehydration. Experiments were performed on conscious nonacclimated and heat-acclimated laboratory rats subjected to various levels of heat stress and/or dehydration (37-42°C with and without drinking water). During the exposures, rectal temperature (T(re)), plasma LA pyruvic acids, and hematocrit were measured. From these data, excess LA, indicative of anaerobic metabolism, was calculated. In separate experiments, transvascular protein efflux (half time of Evans blue- labeled albumin) was measured before and after plasma LA elevation, either by LA infusion or thermal dehydration. The results show that elevation of plasma LA was associated with a rise in T(re), with accelerated elevation within a T(re) range of 41-42°C. LA concentrations were similar for the same T(re) in all experimental groups. In nonacclimated rats, this rise was accompanied by a significant rise in excess LA. In acclimated rats, only a minor rise in excess LA was observed. A positive correlation was found between plasma LA elevation and the increase in plasma protein efflux. It is concluded that there is a temperature threshold for the rise in plasma LA. In nonacclimated rats, local hypoxia may contribute to this rise. The data also suggest that, in nonacclimated rats, lactacidemia accelerates plasma protein and fluid loss, leading to circulatory failure during acute thermal dehydration.
AB - This investigation was undertaken to study heat stress and dehydration effects on 1) plasma lactic acid (LA) concentration and 2) plasma LA effect on plasma volume conservation during thermal dehydration. Experiments were performed on conscious nonacclimated and heat-acclimated laboratory rats subjected to various levels of heat stress and/or dehydration (37-42°C with and without drinking water). During the exposures, rectal temperature (T(re)), plasma LA pyruvic acids, and hematocrit were measured. From these data, excess LA, indicative of anaerobic metabolism, was calculated. In separate experiments, transvascular protein efflux (half time of Evans blue- labeled albumin) was measured before and after plasma LA elevation, either by LA infusion or thermal dehydration. The results show that elevation of plasma LA was associated with a rise in T(re), with accelerated elevation within a T(re) range of 41-42°C. LA concentrations were similar for the same T(re) in all experimental groups. In nonacclimated rats, this rise was accompanied by a significant rise in excess LA. In acclimated rats, only a minor rise in excess LA was observed. A positive correlation was found between plasma LA elevation and the increase in plasma protein efflux. It is concluded that there is a temperature threshold for the rise in plasma LA. In nonacclimated rats, local hypoxia may contribute to this rise. The data also suggest that, in nonacclimated rats, lactacidemia accelerates plasma protein and fluid loss, leading to circulatory failure during acute thermal dehydration.
KW - capillary permeability
KW - excess lactic acid
KW - heat acclimation
KW - lactic acid
UR - http://www.scopus.com/inward/record.url?scp=0026350886&partnerID=8YFLogxK
U2 - 10.1152/jappl.1991.71.6.2434
DO - 10.1152/jappl.1991.71.6.2434
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C2 - 1778943
AN - SCOPUS:0026350886
SN - 0161-7567
VL - 71
SP - 2434
EP - 2439
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 6
ER -